Concentration of onion juice volatiles by reverse osmosis and its effects on supercritical CO2 extraction

Abstract

Supercritical carbon dioxide extraction of onion oil at moderate temperatures produces a product which is characteristic of the fresh flavor of onions. It was attempted to improve extraction efficiency by concentrating the onion juice by reverse osmosis prior to supercritical CO2 extraction. Reverse osmosis was carried out for all combinations of 600, 700, and 800 psi feed pressure and 25 and 35C. The juice was concentrated to 18 °Brix and then subjected to supercritical CO2 extraction. The effect of concentration on the extraction process was evaluated by comparing the yields of extracts from concentrated juice with that of single strength juice. Concentration of onion juice by reverse osmosis improved the efficiency of supercritical CO2 extraction of onion oil and did not alter its characteristic fresh aroma.